A new analysis of 18 hair products used by black women finds that they contain 45 endocrine-disrupting or asthma-associated chemicals, a finding that could help explain why this population suffers from higher rates of chemical exposure and hormone-related health conditions.

“We found multiples of our targeted chemicals in all of our products,” said study lead author Jessica S. Helm, PhD, of the Silent Spring Institute, Newton, Mass., in an interview. “We’re concerned about the additive effect of multiple products being used together.”

According to the study, previous research has found that, compared with white women, U.S. black women have higher urinary levels of chemicals like phthalates and parabens. Black women also have higher rates of asthma and hormone-related health conditions like uterine fibroids and infertility, Dr. Helms said.

The researchers launched their study to better understand the possible role of hair care products in raising chemical levels in black women, Dr. Helm said.

The researchers tested 18 types of hair care products shown by a 2004-2005 survey to be popular among black women: hot oil treatments, anti-frizz products and polishes, leave-in conditioners, root stimulators, hair lotions, and relaxers. Researchers had purchased the products in 2008.

The researchers detected 45 of 66 target chemicals in the samples, including some that are banned in the European Union or regulated in California based on health concerns, according to Dr. Helms.

Most of the products contained parabens and phthalates (both 78%), UV filters (72%), and cyclosiloxanes (67%).